I just bought an 1999 F150.

It runs a little rough and when I put it drive, the truck kind of shakes. There is not a service engine soon.

I replaced the IAC and TPS.

I checked the MAF and they seem to be within specs. I checked to see if the EGR is holding a vacuum and it holds. I sprayed starter fluid around the vacuum fitting and the intake manifold to observe for change in idle - none.. I wiggled all the vacuum connections to observed for idle change - none.No change in idle. I replaced the PCV. I put one of the hearing stethescope to the each fuel injector and hear the pulses from the injector - they are all working.

I took off the throttle body and plenum and cleaned it good. It almost feels and sounds like a misfire but there are no codes.

What do suggest I check next?

 

Spark plugs...

 

See this thread for suggestions:

https://www.f150forum.com/f6/rough-idle-causes-296798/

 

You may have missed the vacuum elbow at the back of the TB. I went past mine several times until I finally hit it with the spray. they are bad to dry-rot.

 

I pulled the elbow in back of the intake manifold. Made sure there was no holes or if it was worn bad. It seems okay.

 

I'd change everything you contaminated with starting fluid. That's going to give you many problems in the near future which can more less, -make you your trucks worst enemy lol.